1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus configured to eject liquid from nozzle openings. In particular, the invention relates to an ink jet type recording head and an ink jet type recording apparatus configured to discharge an ink as the liquid.
2. Related Art
Liquid ejecting apparatuses, typified by an ink jet type recording apparatus such as an ink jet type printer or plotter, include a liquid ejecting head capable of discharging liquid from a liquid storage portion, such as a cartridge or a tank that stores the liquid, as droplets.
Such a liquid ejecting head includes a pressure generation chamber, which communicates with nozzle openings and a pressure generation unit, which changes the pressure of the liquid contained in the pressure generation chamber to discharge liquid droplets from the nozzle openings. For the pressure generation unit installed in the liquid ejecting head, a longitudinal vibration type piezoelectric element, a deflection vibration type piezoelectric element, a heater element, or an element that uses electrostatic force, for example, are used.
The liquid discharged from the liquid ejecting head described above has a viscosity of an appropriate level for discharging, which is determined according to the type of the liquid. The viscosity of the liquid is related to the temperature of the liquid. To paraphrase this, the viscosity rises as the temperature falls and falls as the temperature rises. Therefore, it is necessary to correct a drive signal for driving the pressure generation unit of the liquid ejecting head in accordance with the viscosity that has changed in accordance with the temperature of the liquid. For example, refer to JP-A-6-31934 and JP-A-2009-56669.
However, because the measurement of the liquid temperature is carried out by measuring the external environment outside the liquid ejecting head (i.e., the ambient temperature) by using a temperature sensor, an error may occur in the case where there is a difference between the temperature of the liquid stored in the liquid ejecting head immediately before ejection and the environmental temperature. Accordingly, if the drive signal is corrected on the basis of the environmental temperature, the drive signal will not be corrected to be a drive signal that is optimal for the actual viscosity of the liquid. As a result, the discharge performance may be degraded and the print quality may be degraded.
In addition, a temperature sensor may be arranged in a flow path of the liquid ejecting head but it is difficult to provide such a temperature sensor in the flow path because liquid ejecting heads have become more densely arranged and smaller. In addition, providing a temperature sensor in the flow path may result in an increase in the size of the liquid ejecting head and an increase in the manufacturing cost. Furthermore, it is necessary to insulate the temperature sensor to be provided in the flow path. The insulated temperature sensor may become large. Accordingly, the large temperature sensor cannot be arranged in the flow path. In addition, wiring for connecting the sensor to the outside of the flow path becomes necessary. As a result, a problem that a complex structure is required may arise.